Electro-optically active polymers having pendent aromatic azo-type "transducer" groups can be made by free radical polymerization of monomer having terminal vinyl groups and containing the aromatic azo-type transducer groups. However, it has been found that polymerization yield and the molecular weight of the polymer decrease with increasing amount of transducer groups in the polymer. This is explainable by the chain transfer character of the electron-withdrawing group substituted phenyl ring. Minimization of initiator concentration and lowering of polymerization temperature to increase polymer molecular weight results in lower conversions and impractically long polymerization time. For homopolymers of these monomers containing azo-type "transducer" groups, the molecular weight of the polymer obtained by that route is usually less than about 20,000; the polymer is brittle and difficult to fabricate into useful light modulating devices. Furthermore, the vinyl monomer containing an aromatic azo-type "transducer" with a particular substituent, such as those bearing a hydroxyl group on the aromatic ring, cannot be easily made without the protection of the hydroxy group and the monomer, when finally made, cannot be polymerized by conventional radical method.
The present invention provides a novel method for making high molecular weight polymers having high contents azo-type "transducers" which avoids these difficulties, and thus is capable of providing useful polymers of this type which are inaccessible from the monomer approach.